Removed long time off-line builders and slaves.

Builders:
llvm-mips-linux
perf-x86_64-penryn-O3
clang-openbsd-amd64
perf-x86_64-penryn-O3-polly-fast
perf-x86_64-penryn-O3-polly-parallel-fast
perf-x86_64-penryn-O3-polly-unprofitable
perf-x86_64-penryn-O3-polly
perf-x86_64-penryn-O3-polly-detect-only
lldb-amd64-ninja-freebsd11
clang-native-aarch64-full
clang-bpf-build

Slaves:
pollyperf1, pollyperf2, pollyperf3, pollyperf4, pollyperf5, pollyperf6, pollyperf7, pollyperf11, pollyperf14, pollyperf15,
mipsswbrd002, juno-aarch64-01, bpf-build-slave01, lldb-amd64-ninja-freebsd11, openbsd-amd64